Ceramic-matrix composites (CMC) made of carbon and silicon carbide dual matrix reinforced with carbon fibres (C/C-SiC) have exceptional heat, thermal shock, creep, and wear resistance, while also having little density and high strength. In comparison to monolithic ceramics, CMC possess ductility and damage tolerance, which opens this material for severe applications. Starting in space applications, this material is today well established in friction applications, where lightweight high-performance brakes securely decelerate e.g. luxury cars or elevators. The high production costs still limit the broad application like as brake discs in standard passenger cars, although less weight, better performance and longer lifetime. The industrial used production process is the liquid silicon infiltration (LSI) with it three steps: green body shaping, pyrolysis and silicon infiltration. In this work, the shaping process of the carbon fibre reinforced plastic (CFRP) green body, is done by thermoset injection moulding. The application of plastic production processes like compounding and injection moulding in the liquid silicon infiltration process route, enables large-scale manufacturing. However, the screws and high shear forces inside the plastic processing machines significantly shorten the fibres. This paper describes the pros and cons of thermoset injection moulding in the LSI route, as well as the development and effect of different reinforcement types in dependence of their fibre length, since several energy dissipation mechanisms bases on a minimum length of reinforcement fibres in CMC. Various raw materials like short and chopped fibres with different length, rovings, and different approaches to receive longer fibres and their outcomes are presented. The mechanical properties show promising values and the micrographs display the infiltration status and crack development inside the specimen.

In order to enhance the load capacity, gears can be nitrided. The diffusion zone, measurable by the nitriding hardness depth, is considered to be the parameter governing for the high load-bearing capacity of nitrided gears. The wear behavior of gears is mainly determined by the characteristics (phase, porosity and chemical composition) of the compound layer but the influence of the compound layer on the load carrying capacity is not known yet. In this work, nitriding treatments for gears were developed with the aim to create compound layers with varying thickness, composition and properties in order to ensure a maximum load carrying capacity for nitrided gears.

A compound layer is formed by ingress of nitrogen from an external nitrogen source into the surface layer and the formation of nitrides when the solubility of nitrogen in the bulk material is exceeded. In the surface layer, where the nitrogen concentration is at its maximum level, the nitrides form a closed layer. The compound layer continues to contain alloy nitrides which have formed from the carbides and other precipitates from the bulk material. The properties of the compound layer have a decisive influence on the wear and fatigue behavior of the loaded surfaces. The current investigations deal with the extensive characterization of compound layers that have been produced in heat treatment processes with the aim of producing stress-resistant nitriding layers. The commonly used nitriding and quench and temper (Q&T) steels 31CrMoV9 and 42CrMo4 served as examination material. The structure of the compound layers was varied within the nitriding trials regarding the phase composition, porosity and layer thicknesses. The phase composition of the compound layers was determined by special etching, scanning electron microscopy (SEM), X-ray diffraction and GDOES.

To increase product quality injection molding tools are equipped with innovative tempering technologies. The customers strive for the technology with the lowest energy consumption. Ceramic materials like yttria-stabilized zirconia (YSZ) are able to thermally insulate tool surfaces providing a more precise temperature regulation with intent to shorten cycle times as well as to decrease energy demands during the molding process. High quality ceramic thin films could be applied by metalorganic chemical vapor deposition (MOCVD). Laser machining technologies have been developed for machining the ceramic materials. In this work we demonstrate the fabrication of zirconia based thin films on steel tools via MOCVD using solid metalorganic precursors. Shorter coating times and a solvent free process are some of the advantages of our new developed coating process. The ultrashort pulse laser processing (USPLP) was used to structure the developed MOCVD coating. Using this technology the ceramic material undergoes no thermal stress cracks, because USPLP is characterized by the preference of cold material removal. The laser processing procedure was developed by working out machining parameters for the different materials. The difference between steel and ceramic in the removal behavior was determined immediately so that a machining strategy for the ceramic CVD coating could be designed successfully. The implementation of defined roughness and a carbon fiber like structure in the coating were realized. Coated and laser-structured injection molding tools were tested regarding their desired properties under production conditions.

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